Some asphalt mixes have been proposed in the past that utilize recycled asphalt concrete and are suitable for use in paving at ambient temperatures. (See, for example, Japanese Patent Publication Serial No. 55-19268 (1980). These asphalt mixes are formed by crushing recycled asphalt concrete into aggregate grains to such an extent that each aggregate grain will still retain asphalt on its surface; adding to the aggregate grains an appropriate amount of volatile oil, such as kerosene and light oil, and an appropriate amount of additives including both asphalt emulsion and liquid rubber, at an ambient temperature; and mixing them together. Thus, these asphalt mixes are based on the technical concept that, while these mixes would not congeal within a sealed container, once they are exposed to ambient air at a paving site the volatile oil evaporates to allow asphalt to congeal and harden to form a pavement.
These asphalt mixes are advantageous in that they may be formed without heat treatment during the adding and mixing of the additives to the aggregate grains, as described above, and also in that they may be applied easily at an ambient temperature to form a pavement. However, because the additives include liquid rubber, these mixes cannot harden immediately after their application at a paving site and, rather, take a considerable amount of time, often as long as a few months, before achieving a desired hardness. This presents the further disadvantage that the resulting pavement may be cracked or otherwise damaged prematurely before it achieves sufficient hardness and strength.
To achieve a sufficiently hard pavement surface immediately after paving, the amount of volatile oil to be added to the aggregate grains may be reduced, so as to allow the asphalt to congeal more easily. This, however, makes it almost impossible to store the asphalt mixes, since volatile oil tends to evaporate over time causing the mixes to congeal and lump together. Lumped and solidified mixes thus become unusable later on, when they are to be applied to form a pavement.
Some other asphalt mixes have been also proposed in the past that include a special additive (chemical substance) to cause a polycondensation reaction, so as to increase the hardness of the resulting asphalt pavement after it is solidified. (See, for example, Japanese Patent Publications Serial Nos. 63-137959 (1988) and 2-228363 (1990).) Production of such special additives, however, is extremely cumbersome and expensive, and the strength of the resulting asphalt pavement cannot be expected to improve substantially.
A need exists for an improved asphalt mix that may be applied to form or repair a pavement at an ambient temperature, which can be stored for a long time, and is capable of achieving sufficient strength and stability immediately after its application at a paving site. Such asphalt mix preferably does not require a special additive formed of expensive chemical substances.